When the supply of oxygen is limited during the combustion of a hydrocarbon, carbon monoxide (CO) is produced.

Here's why:

* Complete Combustion: With ample oxygen, hydrocarbons burn completely, producing carbon dioxide (CO2), water (H2O), and energy.

* Incomplete Combustion: When oxygen is limited, the combustion process is incomplete. The carbon atoms in the hydrocarbon don't have enough oxygen to form CO2, resulting in the formation of carbon monoxide (CO).

Carbon monoxide is a colorless, odorless, and highly toxic gas. It's dangerous because it binds to hemoglobin in red blood cells, preventing oxygen from being transported to the body's tissues.